Is Mold in Your Home?

Mold in a house is rarely where people first look for it. In the Triangle, where most homes are built over a crawl space rather than a basement, the place it most often takes hold is under the floor: on joists, subfloor and insulation that nobody sees from one year to the next. You usually notice it upstairs first, as a smell, or as allergies that will not settle down.

The good news is that mold is easier to understand than its reputation suggests. It needs moisture to grow. Control the moisture and you control the mold. Leave the moisture in place and no amount of cleaning will keep it away.

Mildew or Mold?

People use the two words interchangeably, and strictly speaking mildew is a kind of mold. The difference that matters to a homeowner is where it is growing and how deep it goes.

Surface mildew is the gray or black speckling on shower grout, a window sill or a bathroom ceiling. It sits on top of a hard surface, wipes off with a household cleaner, and comes back when the room stays damp. It is a ventilation problem in that one room: run the exhaust fan, open a window, and wipe down wet surfaces.

Crawl space mold is a different situation. It grows on wood, such as floor joists, the subfloor and the band board around the edge of the framing, and on the paper facing of fiberglass insulation, which is usually the first thing to show it. It can be white and fuzzy, green, black or a dusty gray, and it has often been there a long time before anyone sees it. Because the moisture feeding it never lets up, it does not stay a surface problem.

Color does not tell you much. Plenty of harmless molds are dark, and the species people call black mold cannot be identified by looking at it. That takes a lab. Third-party testing will identify it if you want to know, but the species rarely changes what has to be done.

Signs of Mold Under Your House

• A musty or earthy smell in the house, strongest near floor registers, in closets, or in rooms over the crawl space
• A smell that gets worse in summer, or for a day or two after heavy rain
• Allergy symptoms, such as congestion, itchy or watery eyes, or coughing, that ease when you are away from home
• Dark staining or fuzzy growth on floor joists or the underside of the subfloor
• Insulation that is discolored, sagging or falling out from between the joists
• Condensation on ductwork or pipes in the crawl space
• Wood that feels soft when you press it, which can mean rot has followed the mold
• Standing water, wet soil, or a torn or missing vapor barrier

You do not have to see mold to have it. A persistent musty smell on its own is one of the most common signs.

Why Moisture Is Always the Cause

Mold spores are everywhere, indoors and out. They are not the problem. The problem is a surface that stays damp long enough for them to grow. Under a house, that moisture comes from a few places: water vapor rising out of bare soil, humid summer air coming in through the foundation vents and condensing on cool wood and ducts, rain or groundwater getting under the house, and plumbing leaks.

Attics are the other place we find it, and there the cause is usually trapped household air: blocked soffit vents, or a bathroom fan ducted into the attic instead of outside, leaving warm, damp air to condense on the cold underside of the roof deck through the winter.

This is why mold so often comes back to the same joist a year after it was cleaned. The growth was removed, but the conditions that grew it were left exactly as they were.

Why Mold Under the House Matters Upstairs

Air moves up through a house. Warm air escapes through the upper floors and the attic and is replaced by air drawn in from below, which in a crawl space home means from the crawl space. Mold on a joist you have never seen becomes spores and odor in your living room. We explain how that works in Better Air Quality Starts in Your Crawl Space.

How much mold affects people depends on the amount of exposure and on the person. Symptoms range from mild allergy symptoms to sinus congestion, headaches, and eye, nose and throat irritation, and people with allergies or asthma, infants, older adults and anyone with a weakened immune system are most at risk. For the house itself, mold is a sign that wood is staying wet, and wood that stays wet eventually rots. It also tends to turn up in a buyer's home inspection, which is a bad time to find out about it.

How to Keep Mold Out of Your Home

• Run kitchen and bathroom exhaust fans, or open windows, to move moisture outside
• Make sure bathroom fans and your clothes dryer vent to the outdoors, not into the attic or crawl space
• Make sure your attic is properly ventilated, with soffit vents left clear of insulation
• Keep gutters clean and carry downspouts well away from the foundation
• Cover crawl space soil with a sealed vapor barrier, and control the humidity under the house with a crawl space dehumidifier
• Act quickly if your crawl space floods, both to dry it out and to stop it from happening again
• Choose mold-resistant materials where you can, but remember they only help when the rest of the home is properly built, sealed, and maintained

What Proper Removal Looks Like

Dealing with crawl space mold properly is more than spraying what you can see. Our mold removal process contains the work area, removes water- and mold-damaged materials, dries the space, removes fungal growth from the structural wood, and finishes with HEPA vacuuming and air scrubbing. Then comes the part that decides whether you see it again: correcting the moisture, with a vapor barrier, encapsulation, a dehumidifier or drainage work depending on what the inspection finds. Where joists have already been weakened, they get repaired.

Resist the urge to scrub or scrape heavy growth yourself. Disturbing it puts spores into the air, and in a crawl space that air is headed for your house.

Triangle Reconstruction has been removing crawl space mold, and fixing the moisture behind it, across Wake and Durham counties and every county bordering them since 2012. If your house smells musty or you have found growth under the floor, call (919) 924-7600.